JP3696474B2 - Hydraulic control device for continuously variable transmission - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a continuously variable transmission using a V-belt for a vehicle or the like, and more particularly to an improvement in a hydraulic control device thereof.
[0002]
[Prior art]
As a continuously variable transmission suitable for a vehicle, for example, there is a V-belt continuously variable transmission as disclosed in JP-A-11-82725.
In this method, a V-belt is stretched between a primary pulley connected to the engine side and a secondary pulley connected to the axle side, and the groove width of the primary pulley is variably controlled by hydraulic pressure.
The schematic configuration and the hydraulic control apparatus are shown in FIGS.
[0003]
The speed change mechanism 10 in which the V-belt 24 is stretched between the primary pulley 16 and the secondary pulley 26 is connected to an engine (not shown) via a torque converter 12 having a lock-up clutch 11.
The primary pulley 16 forms a V-shaped pulley groove with a fixed conical plate 18 that rotates integrally with the output shaft of the torque converter 12 and a movable conical plate 22 that faces the fixed conical plate 18. And a first cylinder chamber 20 that displaces the movable conical plate in the axial direction.
The secondary pulley 26 forms a V-shaped pulley groove with a fixed conical plate 30 that rotates integrally with an output shaft toward the axle (not shown) and a movable conical plate 34 that faces the fixed conical plate 30. The movable conical plate 34 is urged by a return spring (not shown) in the direction of narrowing the width of the pulley groove, and includes a second cylinder chamber 32 that applies hydraulic pressure to the back surface thereof to displace the movable conical plate 34 in the axial direction. .
[0004]
The transmission mechanism 10 is controlled by the hydraulic control valve 3 based on a signal from the CVT control unit 1.
Line pressure is always supplied from the hydraulic control valve 3 to the second cylinder chamber 32, and the first cylinder chamber 20 is connected to a shift control valve 63 of the hydraulic control valve.
The pressure receiving area of the first cylinder chamber 20 is set larger than the pressure receiving area of the second cylinder chamber 32.
[0005]
The hydraulic pressure applied to the first cylinder chamber 20 is controlled by the shift control valve 63 to change the groove width of the primary pulley 16, while the line pressure is supplied to the second cylinder chamber 32 to control the clamping pressure with respect to the V belt 24. It is like that. As a result, the driving force is transmitted according to the contact frictional force between the V belt 24 and the pulleys 16 and 26.
In terms of the number of rotations, when the groove width of the primary pulley 16 is widened and the contact ratio of the V belt 24 is small and the contact radius on the secondary pulley 26 side is large, the gear ratio is low (low speed side). As the engine speed increases, the engine speed is reduced and output to the axle. At a reverse pulley ratio Hi (high speed side), the gear is output with a small gear ratio. During this time, the gear ratio changes continuously corresponding to the contact radius ratio between the primary pulley 16 and the secondary pulley 26.
[0006]
In the hydraulic control valve 3, the line pressure obtained by adjusting the hydraulic pressure from the hydraulic pump 80 by the line pressure regulator 60 is constantly supplied to the second cylinder chamber 32 and is also supplied to the shift control valve 63. The hydraulic pressure to the first cylinder chamber 20 is controlled by driving the speed change control valve 63 with a step motor 64 using the line pressure as a source pressure.
The hydraulic control valve 3 further includes a line pressure solenoid 4, a pressure modifier 62, and a pilot valve 61.
[0007]
In addition to the select position signal from the inhibitor switch 8, the CVT control unit 1 provides necessary lines based on the engine torque estimated from the throttle opening (accelerator pedal opening) TV0 and the engine speed Ne from the throttle opening sensor 5. The pressure is obtained, and a duty ratio signal corresponding to the pressure is output to the line pressure solenoid 4 and a shift command is output to the step motor 64.
For example, the position of the step motor 64 in the range of 20 to 170 steps corresponding to the target gear ratio within a range of 200 steps is selected.
[0008]
The line pressure solenoid 4 supplies the hydraulic pressure from the pilot valve 61 to the pressure modifier 62 side according to the duty ratio signal from the CVT control unit 1, and the line pressure regulator 60 supplies the hydraulic pressure from the hydraulic pump 80 from the pressure modifier 62. Set the line pressure according to the output hydraulic pressure. Thus, the line pressure is changed within a predetermined range according to the required transmission driving force and is output.
[0009]
The speed change control valve 63 is driven by the spool 63a according to the displacement of the speed change link 67 spanned between the movable conical plate 22 of the primary pulley 16 and the step motor 64, and adjusts the line pressure from the line pressure regulator 60 to adjust the line pressure. Supply to one cylinder chamber 20. Thereby, the groove width of the primary pulley 16 is variably controlled to obtain a predetermined gear ratio.
The CVT control unit 1 is connected to a first rotational speed sensor 6 and a second rotational speed sensor 7 that detect the rotational speeds of the primary pulley 16 and the secondary pulley 26, and in the transmission mechanism unit 10 based on these detection signals. A transmission ratio is required.
In addition to the above, the details of the overall configuration of FIGS. 2 and 3 are cited from Japanese Patent Laid-Open No. 11-82725.
[0010]
[Problems to be solved by the invention]
By the way, the line pressure supplied to the transmission control valve 63 and the second cylinder chamber 32 needs to be set to a value capable of obtaining a reliable torque transmission between both pulleys. There is a problem that the friction loss due to the contact friction force between the V-belt 24 and the pulleys 16 and 26 is increased, and the fuel consumption is deteriorated.
Therefore, it is common to control the line pressure with high accuracy so that the minimum oil pressure is always capable of transmitting torque.
[0011]
However, for example, in a light accelerator pedal depression state where the accelerator opening is about 1/8, there is a problem that the shift to the Hi side is not easily achieved, and the shift stops in the middle, and the shift width is actually narrowed. Arise.
That is, in order to maintain the current gear ratio in the transmission mechanism unit 10, the ratio of thrust in the direction of narrowing the groove width of the movable conical plates 22, 34 in the primary pulley 16 and the secondary pulley 26 is set to each cylinder. It is necessary to have a predetermined relationship based on the pressure receiving area of the chamber, and when the thrust of the primary pulley 16 falls below this relationship, the gear ratio is likely to shift to the Low side.
[0012]
The thrust of the primary pulley 16 is almost determined by the hydraulic pressure to the first cylinder chamber 20, but the thrust on the secondary pulley 26 side is input by the return spring and the V belt 24 in addition to the thrust by the hydraulic pressure to the second cylinder chamber 32. Since the thrust based on the torque is added, the line pressure is set to a very low value (usually the minimum hydraulic pressure value) when the transmission torque is about 1/8 of the accelerator opening, and the hydraulic pressure in the cylinder chamber is The influence of thrust other than hydraulic pressure becomes relatively large, and the thrust relationship cannot be maintained.
Therefore, in view of the above-described problems, the present invention provides a hydraulic control device for a continuously variable transmission that reduces friction loss between a belt and a pulley and improves fuel consumption performance while allowing shift to the Hi side as designed. The purpose is to do.
[0013]
[Means for Solving the Problems]
The first aspect of the present invention is a transmission mechanism comprising a pair of variable pulleys each having a first and a second cylinder chamber, supplied with hydraulic pressure and capable of changing the groove width, and a belt stretched between the variable pulleys. A line pressure supply means that generates a line pressure and constantly supplies the line pressure to the second cylinder chamber, and a shift control valve that is driven by an actuator and supplies a hydraulic pressure with the line pressure as an original pressure to the first cylinder chamber And a shift control unit that outputs a shift command for controlling the actuator based on the driving state and changes the line pressure output from the line pressure supply unit. a shift achieve detection means for detecting a gear shift progress with respect to the command, to increase the line pressure by the line pressure supply means when shifting to high-speed side is not achieved by the shift control valve It was the thing.
If the speed change is not achieved even if the speed change command is output to the actuator, the line pressure increases and the speed change is realized. Therefore, the hydraulic pressure before the speed change is set to a low value with little friction loss in the speed change mechanism. The low set value is maintained as long as the shift is achieved.
[0014]
The invention of claim 2 is provided with a step motor that drives the actuator to a position corresponding to the target gear ratio, and the shift control means further adds the step motor to each predetermined additional step when shifting to the high speed side is not achieved. Driven, the line pressure is increased when the number of additional steps reaches a predetermined value without shifting being achieved.
After confirming that shifting is not achieved even if the step motor is driven until the specified number of additional steps is reached, that is, after confirming the dead state, the hydraulic pressure is increased, so the line pressure immediately fluctuates with some response delay. In addition, since the number of additional steps is set to a predetermined value and the insensitive state confirmation time does not fluctuate, stable control characteristics can be obtained.
[0015]
According to a third aspect of the present invention, the actuator includes a step motor that is driven to a position corresponding to the target gear ratio, and the shift control means further drives the step motor by a predetermined additional step when shifting to the high speed side is not achieved. Thus, the line pressure is increased when the position of the step motor reaches a position corresponding to the highest speed gear ratio without achieving a shift.
If the shift is not achieved, the hydraulic pressure is not immediately increased and the additional step is driven, so that the line pressure is not fluctuated with a slight response delay as in the third aspect of the invention. On the other hand, since the driving of the additional step is performed until the position corresponding to the highest speed gear ratio is reached, it is not necessary to count the number of additional steps and the calculation load is reduced.
[0016]
In each invention, the shift achievement detecting means may detect the shift achievement status by comparing the rotation speed ratio between the pair of variable pulleys and the target gear ratio, as in claim 4.
[0017]
In the invention of claim 5, when the shift control means detects that the shift is achieved by the shift achievement detecting means after increasing the line pressure, the line pressure is further returned to the level before the increase. It is.
Since the hydraulic pressure is returned to the level before the increase after the shift is achieved, the hydraulic pressure supplied to the transmission mechanism unit is always maintained at a value with a small friction loss, except for the minimum period necessary to achieve the shift.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described by way of examples.
In the present embodiment, when the line pressure is controlled by the CVT control unit 1 in the configuration shown in FIGS. 2 and 3, first, the minimum hydraulic pressure is controlled as the first set value that is the minimum necessary value corresponding to the transmission torque. If the target gear ratio is not achieved even if the stepping motor 64 is controlled to shift to the Hi side, the minimum hydraulic pressure is switched to the second set value higher than the first set value. Other configurations are the same as those shown in FIGS.
[0019]
FIG. 1 is a flowchart showing a control flow in the CVT control unit 1 and an operation of the hydraulic control valve 3.
In the line pressure regulator 60, the hydraulic control valve 3 has a maximum hydraulic pressure of about 4 MPa from the lowest hydraulic pressure of the first set value, for example, 0.6 MPa, in accordance with the command from the CVT control unit 1 according to the command from the hydraulic pump 80. Output as a line pressure that varies with the range.
The hydraulic pump 80, the line pressure solenoid 4, the pressure modifier 62, the pilot valve 61 and the line pressure regulator 60 constitute the line pressure supply means of the invention.
[0020]
First, in step 101, when the target gear ratio is determined by the CVT control unit 1 (shift start), a standard step position of the step motor 64 corresponding to the target gear ratio is calculated in step 102, and the current position and Is output to the step motor 64 as a shift command. Here, the shift to the Hi side is considered.
In step 103, the number of additional steps for subsequent control is set to n = 0.
[0021]
In step 104, the step motor 64 moves by the number of steps of the shift command, and the shift control valve 63 is actuated via the shift link 67 accordingly, and the position of the primary pulley 16 movable conical plate 22 changes and the V belt 24 is moved. The contact radius changes.
In the next step 105, the CVT control unit 1 reads the rotational speeds of the primary pulley 16 and the secondary pulley 26 from the first rotational speed sensor 6 and the second rotational speed sensor 7, and calculates the actual gear ratio.
[0022]
In step 106, the actual gear ratio is compared with the target gear ratio to check whether or not the gear shift is completed. If the shift is not completed, that is, if the shift has not been reached, the routine proceeds to step 107.
In step 107, n = n + 1 is set as the additional step number for the shift command, and then in step 108, it is checked whether the additional step number n has exceeded a predetermined threshold value (for example, 15).
[0023]
Here, if n ≦ 15, the routine proceeds to step 109 where a shift command for one step is output from the CVT control unit 1 to the step motor 64, and then the routine returns to step 104.
When n exceeds 15 in the check of step 108, the process proceeds to step 110, and the minimum oil pressure of the line pressure controlled from the CVT control unit 1 through the line pressure solenoid 4 is changed from the first set value to the second set value. Correction to change to is performed, and the process returns to step 104.
[0024]
When it is confirmed in step 106 that the shift has been completed, in step 111, a process of returning the minimum hydraulic pressure of the line pressure to the first set value is performed and the process ends.
[0025]
Thus, normally, the minimum hydraulic pressure of the line pressure is set as the first set value lower than the second set value necessary for obtaining reliable torque transmission, and the step motor 64 is driven based on the standard step position at the time of shifting. However, if it does not shift to the Hi side as the target, the number of drive steps of the step motor 64 is further increased by one step, and the control ends when the target gear ratio is achieved.
[0026]
On the other hand, if the insensitive state that does not shift to the Hi side continues even if the drive step is increased until the number of additional steps reaches the threshold value, the minimum hydraulic pressure is changed to the second set value higher than the first set value, Make sure to shift to the Hi side. As a result, when the target gear ratio is reached, the minimum hydraulic pressure of the line pressure is returned to the first set value again.
The CVT control unit 1 constitutes a shift control means in the invention, and step 106 in the control flow by the CVT control unit 1 constitutes a shift achievement detecting means.
[0027]
The embodiment is configured as described above, and the minimum line pressure is the first set value that reduces the friction loss between the belt 24 and the pulleys 16 and 26, and only when the shift to the Hi side is not achieved at the time of shifting. Since the minimum hydraulic pressure is raised to the second set value and returned to the first set value when shifting is possible, the minimum hydraulic pressure is kept at the first set value as much as possible to shift to the Hi side. And high fuel efficiency is obtained.
[0028]
In the above embodiment, the number of additional steps is calculated until the threshold value is reached to check the insensitive state. Instead of performing the calculation, the step motor 64 is driven at the highest speed by repeating the driving by the additional step. When the position corresponding to the gear ratio is reached, the minimum hydraulic pressure may be increased to the second set value. Thereby, the calculation load in the CVT control unit 1 is reduced.
[0029]
Further, although the embodiment has been described based on the device described in Japanese Patent Laid-Open No. 11-82725, the present invention is not limited to an engine-driven vehicle in which the primary pulley of the transmission mechanism unit is directly connected to the torque converter, The present invention can be applied to various types of vehicles.
For example, in a hybrid vehicle that includes an engine and an electric motor as drive sources, the speed change mechanism may be connected to the electric motor.
Further, the hydraulic source of the hydraulic control valve is not limited to the hydraulic pump driven by the engine, and a hydraulic pump driven by the drive source electric motor or a dedicated motor may be used.
[0030]
【The invention's effect】
As described above, the present invention includes a speed change mechanism portion in which a belt is stretched over a pair of variable pulleys each provided with a cylinder chamber, and the line pressure is constantly supplied to one cylinder chamber and is driven by an actuator. in the hydraulic control apparatus for a CVT in a hydraulic pressure source pressure to the line pressure through the shift control valve is supplied to the other cylinder chamber to change the groove width of the variable pulley performs a shift, the high-speed side in the shift control valve Since the line pressure is increased when shifting to is not achieved, the hydraulic pressure before shifting can be set to a low value with little friction loss in the shifting mechanism, and high fuel efficiency can be obtained while reliably shifting. It has the effect.
[0031]
In particular, when the actuator is provided with a step motor that is driven to a position corresponding to the target gear ratio, and the shift to the high speed side is not achieved, the step motor is further driven by a predetermined additional step, and the shift is not achieved. By increasing the line pressure when the number of steps reaches a predetermined value, a stable control characteristic can be obtained without changing the line pressure with a slight response delay.
[0032]
Alternatively, instead of increasing the line pressure when the number of additional steps reaches a predetermined value, the step motor is driven by a predetermined number of additional steps, and the position of the step motor corresponds to the highest speed gear ratio without shifting being achieved. Similarly, stable control characteristics can be obtained by increasing the line pressure when the pressure reaches. In this case, it is not necessary to count the number of additional steps, and there is an advantage that the calculation load is reduced.
[0033]
In addition, when it is detected that the shift is achieved after increasing the line pressure, the line pressure is further returned to the level before the increase, except for the minimum period necessary to achieve the shift, Since the hydraulic pressure supplied to the transmission mechanism is always maintained at a value with little friction loss, the fuel efficiency can be further improved.
[Brief description of the drawings]
FIG. 1 is a flowchart of control in a CVT control unit according to an embodiment of the present invention.
FIG. 2 is a diagram showing a schematic configuration of a V-belt type continuously variable transmission showing an application target of the present invention.
FIG. 3 is a diagram showing a hydraulic circuit in the continuously variable transmission of FIG. 2;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 CVT control unit 3 Hydraulic control valve 4 Line pressure solenoid 6 1st rotation speed sensor 7 2nd rotation speed sensor 8 Inhibitor switch 10 Transmission mechanism part 12 Torque converter 16 Primary pulley 18 Fixed cone plate 20 1st cylinder chamber 22 Movable cone plate 24 V belt 26 Secondary pulley 30 Fixed conical plate 32 Second cylinder chamber 34 Movable conical plate 60 Line pressure regulator 61 Pilot valve 62 Pressure modifier 63 Shift control valve 63a Spool 64 Step motor 67 Shift link 80 Hydraulic pump

Claims (5)

A transmission mechanism portion comprising a pair of variable pulleys each having a first and second cylinder chamber and supplied with hydraulic pressure to change the groove width, and a belt stretched between the variable pulleys;
Line pressure supply means for generating line pressure and constantly supplying the line pressure to the second cylinder chamber;
A shift control valve that is driven by an actuator and supplies a hydraulic pressure with a line pressure as an original pressure to the first cylinder chamber;
A hydraulic control device for a continuously variable transmission that includes a shift control unit that outputs a shift command for controlling the actuator based on an operating state and changes a line pressure output from the line pressure supply unit.
The shift control means has a shift achievement detecting means for detecting a shift achievement status with respect to a shift command, and when the shift control valve does not achieve a shift to the high speed side, the line pressure supply means increases the line pressure. A hydraulic control device for a continuously variable transmission. The actuator includes a step motor that is driven to a position corresponding to a target gear ratio,
The shift control means further drives the step motor by a predetermined additional step when shifting to the high speed side is not achieved, and the line pressure when the number of additional steps reaches a predetermined value without achieving shifting. The hydraulic control device for a continuously variable transmission according to claim 1, wherein The actuator includes a step motor that is driven to a position corresponding to a target gear ratio,
The shift control means further drives the step motor by a predetermined additional step when the shift to the high speed side is not achieved, and the position of the step motor reaches the position corresponding to the maximum speed ratio without achieving the shift. 2. The hydraulic control device for a continuously variable transmission according to claim 1, wherein the line pressure is sometimes increased. 4. The continuously variable transmission according to claim 1, wherein the shift achievement detecting means detects a shift achievement state by comparing a rotation speed ratio between the pair of variable pulleys with a target gear ratio. Hydraulic control device. The shift control means returns the line pressure to the level before the increase when it is detected that the shift is achieved by the shift achievement detecting means after increasing the line pressure. 3. A hydraulic control device for a continuously variable transmission according to 3 or 4.

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